Metabolic, hygric and ventilatory physiology of a hypermetabolic marsupial, the honey possum (Tarsipes rostratus)

The honey possum is the only non-volant mammalto feed exclusively on a diet of nectar and pollen. Likeother mammalian and avian nectarivores, previous studiesindicated that the honey possum’s basal metabolic rate washigher than predicted for a marsupial of equivalent bodymass. However, these early measurements have been questioned.We re-examined the basal metabolic rate(2.52 § 0.222 ml O2 g¡1 h¡1) of the honey possum andconWrm that it is indeed higher (162%) than predicted forother marsupials both before and after accounting for phylogenetichistory. This, together with its small body mass(5.4 § 0.14 g; 1.3% of that predicted by phylogeny) may beattributed to its nectarivorous diet and mesic distribution.Its high-basal metabolic rate is associated with a high-standardbody temperature (36.6 § 0.48°C) and oxygen extraction(19.4%), but interestingly the honey possum has a highpoint of relative water economy (17.0°C) and its standardevaporative water loss (4.33 § 0.394 mg H2O g¡1 h¡1) isnot elevated above that of other marsupials, despite itsmesic habitat and high dietary water intake.